Ca2+ release mechanisms in cardiac & skeletal muscle

OBJECTIVES• Methodology:

• Chimeric proteins• FRET

• Differences in Ca2+ release between cardiac and skeletal muscle

INTRODUCTION

Ca2+ channel characteristics

Voltage sensitive Ca2+ channel molecular structure

Mammalian Ca2+ channel genes

SR Ca2+ release channel – Ryanodine receptor (RyR)

RyR molecular structure

Mammalian ligand-gated Ca2+ channel genes

DHPR-RyR molecular arrangment

Ca2+ release in skeletal muscle

Ca2+ release in cardiac muscle

DISCUSSION

1.5 nA

15 nA

10 nA

Cardiac sequenceSkeletal muscle sequence

pCac6 (Sk)

pCARD1

pCac6 (Sk)

pCARD1

Ca2+ + 0 / Cd2+

CELL SHORTENING

Cardiac sequenceSkeletal muscle sequence

I II III IV

II-III LOOP

Serine687 to alanine (S687A)Serine – PKA (only in Sk)

I II III IV

II-III LOOP

Dyspedic myotubes

Region with RyR-2 cDNA

injection

Normal myotubes

Dyspedic myotubes with RyR-2

Ca2+ transient during spontaneous contractions

Normal myotubes Dyspedic myotubes with RyR-2

Ca2+ currentRyR-2

expressing Dyspedic myotubes

Ca2+ current & [Ca2+]i

RyR-2 expressing Dyspedic myotubes

Ca2+ currentCSk3

expressing Dyspedic myotubes

Ca2+ transientDyspedic myotubes

Electrically evoked

Spontaneous

Failure (electrical)